The invention relates to a disc brake for a commercial vehicle as per the preamble of claim 1. The invention also relates to a brake pad set.
In the case of a generic disc brake, also known as a sliding-caliper brake, in a braking situation, an action-side brake pad is pressed against a vehicle-side brake disc by way of an application device, which is actuable pneumatically or by electric motor. During the further course of the braking process, the brake caliper is, relative to the brake disc, displaced counter to the application direction of the action-side brake pad, causing the opposite, reaction-side brake pad to be driven along and pressed against the other side of the brake disc.
In the case of the known disc brake, after a release of the brake, the brake caliper remains in said position, in which the brake pads, or at least the reaction-side brake pad, lies against the brake disc duly without pressure but with a rubbing action. The residual rubbing torques of the brake pads that thereby arise during driving operation have a disadvantageous effect because they lead to increased fuel consumption and to a reduction of the service life of the components involved, specifically of the brake disc and of the brake pads.
It is duly the case that the brake pads are released slightly during driving operation for example as a result of a wobbling movement of the brake disc and as a result of vibrations and lateral accelerations during cornering. These effects are however not sufficient to prevent said residual rubbing torques in an effective manner.
To counteract this problem, the generic DE 10 2007 001 213 discloses a disc brake having a resetting device which is arranged in one of the guide beams by way of which the brake caliper is displaceably held on the brake carrier, which resetting device has a resilient resetting element by means of which the brake caliper is displaced into an initial position.
This construction has proven successful in principle. However, the use of said known resetting device can lead to problems in the case of compressed-air-actuated disc brakes of heavy commercial vehicles, because here, there are wide-ranging influences resulting from component tolerances and component deformations, which have the effect that reliable functioning of said resetting device is not permitted in all situations.
Similar problems arise in the case of a disc brake such as that to which DE 10 2012 006 111 A1 relates. Here, a resetting device is arranged on the side which is situated opposite the application device and which faces toward the reaction-side brake pad, whereby effective, in particular automatic resetting of the brake caliper is realized, with a simultaneously minimal effect on the system rigidity.
In any case, the resetting device acts on the brake caliper, wherein the brake carrier functions as a counterbearing.
DE 43 01 621 A1 describes a floating-caliper disc brake having a positionally static brake carrier which has two carrier arms which project over the outer edge of a disc brake, having brake shoes which are arranged on both sides of the brake disc and which have in each case one friction pad and one rear plate and which are supported displaceably on the carrier arms, having a floating caliper which is guided axially displaceably on the brake carrier and which engages around the brake shoes and has an actuating device designed for pressing the brake shoes against the brake disc, having a spring arrangement which acts axially on the brake shoes in a brake release direction and which, after the braking operation, assists in the setting of an air gap between the brake shoes and the brake disc. The spring arrangement has at least one spreading spring which is fastened in altogether non-displaceable fashion in an axial direction to a carrier arm of the brake carrier, in that the fastening is performed to a section of the carrier arm situated over the outer edge of the brake disc, and in that the spreading spring has at least two spring arms which lie resiliently in an axial direction against the rear plates of the brake shoes.
US2014/0339026 A1 describes a spreading spring comprising a locking arm which connects the spreading spring to a brake component, a retraction arm; and a preload device which is arranged between the locking arm and the retraction arm, wherein the preload device comprises six or more spiral-shaped loops which store energy during a braking activation and which retract the brake components (brake pad) as soon as the braking process has ended. A brake caliper in the form of a floating caliper, which is not a sliding caliper, is specified. This is suitable for a passenger vehicle but not for a commercial vehicle.
The invention is based on the object of further developing a disc brake of the generic type such that, with the simplest structural means, the service life in particular of the brake pads and of the brake disc is lengthened, and the operating costs are altogether lowered.
A further object consists in providing a corresponding brake pad set.
Said object is achieved by way of a brake disc according to embodiments of the invention.
The further object is achieved by way of a brake pad set according to embodiments of the invention.
A disc brake according to the invention for a commercial vehicle, having a brake caliper which engages over a brake disc and which is in the form of a sliding caliper and which is fastened to a positionally static brake carrier and which has a central opening over the brake disc, comprises two brake pads which are arranged in the brake caliper and which are movable in opposite directions and which have in each case one pad carrier plate and one friction pad fastened thereto and of which an action-side or application-side brake pad can be pressed against the brake disc by way of an application device via at least one brake plunger, and comprises at least one resetting device by means of which the brake caliper can be reset after a braking-induced displacement and release of the brake, wherein the resetting device has a spreading device which engages on the opposite brake pads and which acts equally counter to the respective application direction and which has resilient spreading elements which engage on the respective pad carrier plate. The spreading device is arranged in the central opening, wherein the spreading elements engage, outside the friction pads, directly or indirectly on one side in the center region, or at least two abutment regions arranged spaced apart from one another relative to the center, of the brake pads, wherein the abutment regions have in each case one abutment surface and one bearing surface on which the spreading elements are movably arranged.
By means of the design of the disc brake according to the invention, synchronous resetting of both brake pads and resetting of the brake caliper when the brake is released are realized, wherein the synchronicity relates both to the resetting forces and to the resetting travels. Here, the resetting force acts counter to the respective application direction of the two brake pads, that is to say, in the case of the reaction-side brake pad, toward the caliper rear section, and in the case of the action-side brake pad, toward the caliper head, with gaps with respect to the brake disc being formed.
The spreading device expediently engages on the two brake pads at the pad carrier plates, specifically on the side facing toward the friction pad fastened thereto or on the opposite rear side. To prevent jamming of the respective brake pad during the resetting movement, the spreading element engages either centrally on an upper exposed edge region of the pad carrier plate or symmetrically on two abutment regions to the right and to the left.
A brake pad set according to the invention for the disc brake according to the invention has at least two brake pads with in each case one pad carrier plate and with a friction pad attached to the pad carrier plate, and has the spreading device as indicated above. The pad carrier plate have, outside the friction pads and on one side in the center region or at at least two abutment regions arranged spaced apart from one another relative to the center, in each case one abutment surface and one bearing surface. This yields the advantage that multiple functions (axial and radial transmission of spring force, spring end guidance) are realized in a small space.
In one embodiment, the spreading elements extend, proceeding from a central region in the center of the opening, from the inside to the outside to the abutment regions which are arranged spaced apart from one another relative to the center. It is also possible for the spreading elements to extend, proceeding from a central region in the center of the opening, from the inside to the outside to the abutment regions which are arranged spaced apart from one another uniformly relative to the center.
In this way, the spreading device is arranged in the center in the brake caliper, wherein said spreading device is likewise arranged within an envelope of a wheel rim of an associated wheel.
The two spreading elements are connected to one another in the center (in relation to the carrier horns). It is thus possible to ensure a spring force which is identical—in a small tolerance range—both on the run-in side and on the run-out side. Different spring forces between run-out side and run-in side, which can lead to oblique wear, can be minimized by way of the unilateral engagement of in each case one spring per pad.
A further embodiment provides that the central region of the opening extends to both sides of a virtual center of the opening approximately parallel to the plane of the brake disc over a length in a range from 30 to 50% of a longitudinal axis of the opening. This yields an advantageous adaptation of the spring forces.
In another embodiment, the spreading device has spring arms, of which in each case two lie against an associated pad carrier plate, wherein the spring arms are connected to one another in the central region of the opening, which simplifies installation during assembly and maintenance work.
According to a further concept of the invention, the spreading device has oppositely acting spreading elements, preferably with elastic action, in particular in the form of spring elements.
In the simplest form, a compression spring in the form of a helical spring or leg spring is arranged between the two brake pads, wherein the leg spring is mounted in the center above the brake disc, for example on a pad retaining stirrup by means of which the two brake pads can be pushed under preload into a pad slot. In principle, with the use of a helical spring, the attachment of the ends thereof to the pad carrier plates is sufficient to realize the spreading function to an adequate extent.
According to a further concept of the invention, the spreading device is operatively connected not to the pad retaining stirrup but to the brake carrier, which forms a counterbearing and in which the brake pads are mounted so as to be displaceable coaxially with respect to the brake disc.
For this purpose, a retaining bow is provided which extends over the brake disc in the circumferential region as far as brake carrier horns of the brake carrier which delimit a pad slot on both sides, which retaining bow is, in relation to the thickness of the brake disc, arranged in the center relative to said brake disc. The retaining bow is not the pad retaining stirrup, but is an additional component which is not attached to the pad retaining stirrup.
In one embodiment, the retaining bow may be attached to two mutually oppositely situated stirrups which are connected to the brake carrier, which permits simple attachment.
Alternatively, the retaining bow may be connected to at least the two brake carrier horns of a pad slot, whereas the spreading elements, which engage on the two brake pads, are connected to the retaining bow. Said retaining bow thus forms a centering device which, in correspondence with the brake carrier as a fixed bearing, may also be realized in some other way in terms of construction.
The retaining bow is preferably of C-shaped form in terms of its contour, with a center limb which extends over the brake disc to the extent mentioned and with two end limbs which are angled in the same direction as said center limb toward the brake carrier horns and of which in each case one is fastened to a brake carrier horn of the corresponding pad slot.
By way of the retaining bow to which the spreading device is fastened by way of its spring arms, automatic centering of the brake caliper after a release of the brake, that is to say after the ending of a braking process, is realized, wherein, by way of the thus fixed positioning of the spreading device, the brake pads are reset such that the brake caliper is centered relative to the brake disc.
Furthermore, the spreading device is designed so as to act over the entire range of wear of the brake pads.
Since the points of force engagement on the brake pads change with progressive wear, those functional parts of the spreading device which make contact with the brake pads are designed so as to be supported in sliding fashion on the pad carrier plate of the respective brake pads.
To ensure secure retention of the spring limbs, or, in the case of a different design variant, of the spring arms, even under the action of vibrations during driving operation, the spring arms are supported on the upper edge of the pad carrier plate in relation to the base of the pad slot, likewise in sliding fashion as described above.
With corresponding design of the spreading device, it is moreover possible to dispense with the use of pad retaining springs, which, as is known from the prior art, are fastened to the upper edge of the pad carrier plates and on which a pad retaining stirrup is supported, such that the respective brake pad is retained under preload in the pad slot of the brake carrier.
The structural realization of the spreading device according to the invention may differ in terms of construction, wherein a major advantage emerges from the fact that it is possible to substantially dispense with moving components, self-evidently with the exception of the resilient spreading elements which, for their function, perform a resilient deflection.
The omission of moving parts that is now possible self-evidently has the effect of lengthening the service life of the spreading device, as does the low number of components required, resulting, moreover, in extremely inexpensive production and assembly.
In a further embodiment, each spring arm is formed, at the end, with a fork-shaped spring end such that a support limb and a thrust-imparting limb are formed, wherein the support limb lies movably on a bearing surface of a narrow side of the pad carrier plate, and the thrust-imparting limb lies movably with pressure against an abutment surface of that side of the pad carrier plate which faces toward the friction pad. In this way, an advantageous simultaneous functionality is possible, specifically in that the spring arm can not only introduce thrust forces via the abutment surface into the pad carrier plate but is also guided displaceably in terms of its movements by the abutment surface and the bearing surface. It is furthermore possible for the brake pad to be retained resiliently in its brake pad slot by way of the spring force that is introduced into said brake pad via the bearing surface.
In one embodiment, the bearing surface may be arranged at an angle with respect to a horizontal, wherein the angle lies in a range from 3 to 15°.
In another embodiment, the abutment surface may protrude from the pad carrier plate or be formed into the pad carrier plate. An advantageous adaptation to different brake designs is thus possible.
Furthermore, a projection may be provided on the abutment surface, wherein the projection protrudes from the abutment surface into a slot between the support limb and the thrust-imparting limb. This can permit precise guidance and improved transmission of force.
In an alternative embodiment, each spring arm is formed, at the end, with a spring end with a thrust-imparting limb, wherein the thrust-imparting limb is in contact with a support section of that side of the pad carrier plate which faces toward the friction pad, wherein the thrust-imparting limb, by way of an abutment section, lies movably with pressure against an abutment surface of the support section of the pad carrier plate, and at the same time, by way of a bearing section, lies movably on a bearing surface of the support section of the pad carrier plate. This yields the advantage that two functions can be realized in the thrust-imparting limb, specifically transmission of spring force in an axial and in a radial direction to the brake pad, with simultaneous guidance of the spring end and a saving of structural space and material.
In an alternative refinement, a thrust-imparting limb and a support limb at right angles thereto may be formed in the manner of an angled lug, which can reduce a structural space.
In one embodiment, it is preferable for the support section with the abutment surface and the bearing surface to be formed into the pad carrier plate. This is advantageous because it results in a saving of space and material.
The bearing surface of the abutment regions may be arranged at an angle with respect to a horizontal, wherein the angle lies in a range from 3 to 15°. Guidance of the spring end is improved in this way.
If the abutment surface protrudes from the pad carrier plate or is formed into the pad carrier plate, it is thereby possible to realize an advantageous adaptation to different installation situations.
It is also possible for a projection to be provided on the abutment surface, wherein the projection protrudes from the abutment surface. More precise guidance of the spring end is thus possible.
A particularly advantageous embodiment can be made possible if the abutment regions have a support section which, with the abutment surface and the bearing surface, is formed into the pad carrier plate. This yields a saving of space and material.
In a particularly preferred embodiment, it is provided that the abutment surface runs so as to be offset, in a direction pointing away from the friction pad, relative to that side surface of the pad carrier plate which is equipped with the friction pad. This yields advantageous guidance of the spring end in the pad carrier plate together with a transmission of spring force in a small installation space.                The spreading device comprises two spreading elements, wherein a first spreading element acts on a first pad and a second spreading element acts on a second pad. The two spreading elements are connected to one another in the center (in relation to the carrier horns). It is thus possible to ensure a spring force which is identical—in a small tolerance range—both on the run-in side and on the run-out side. Different spring forces between run-out side and run-in side, which can lead to oblique wear, are minimized by way of the unilateral engagement of in each case one spring per pad.        A uniform application of force by the springs on the action side and on the reaction side, or on the thrust-piece side and on the caliper side, can be realized by way of a flexible adjustment of the center web. Furthermore, it is possible for slight incorrect geometrical positioning of disc, pad and carrier to be compensated by way of the flexible center web.        By way of the center web, it is possible for the active resetting device to be easily positioned and held down by the pad retaining stirrup. It is advantageously possible, during a pad change, for the resetting device to be easily removed and also exchanged.        Through the utilization of the entire pad slot between the carrier horns, it is possible for use to be made of spreading elements or springs with a relatively low spring rate in order to impart relatively constant forces in the event of pad wear. Owing to the long spring travels, the spring elements can be tolerant with regard to spring forces. The spring travels lead to a constant spring rate with low tolerances.        In a preferred design variant, only two springs are used.        The spreading elements may be formed from inexpensive and geometrically flexible metal sheets.        As a result of the offset with different centers of rotation, it is possible to replicate a relatively low spring rate (see patent 4943—FIG. 2). There is advantageously no need for a large number of windings (expensive, bulky).        
Further advantages are:
Adjustability (of the centering)
Spring constants adaptable for each pad side, hence different for inside/outside and better adaptable to surroundings—within limits
Installation by way of center centering stirrup—compensates uneven force build-up
Possible “active” caliper centering
Active pad suspension by way of “fork” on the end of the spider
Another embodiment provides that each spring arm is formed, at the end, with a spring end with a fastening section which, in its longitudinal direction, is formed with an elongated hole which is a guide section for the spring end of the spreading device. In this way, guidance during relative movements between the spring arms and the brake pads can be improved, and a lift-off of the spring arms can be prevented.
Here, each fastening section may lie in each case on a bearing surface of a respective pad carrier plate, wherein the elongated holes of each fastening section interact in each case with an abutment section of the pad rear plate. This yields a simple and effective construction.
For example, a pin fixedly connected to the pad carrier plate may have the abutment surface, which interacts with the respective elongated hole, of the pad carrier plate, wherein the bearing surfaces run in each case tangentially with respect to the brake disc and lie in a plane. A pin is an inexpensive, high-quality component, and can be easily installed.
In one alternative, the elongated holes may form a guide opening which interacts with a contour of the pad carrier plate, wherein the contour is formed as a peg or a projection. Such contours can be easily integrally cast in the case of the pad carrier plate being produced as a cast part. Here, it is possible for the contour to protrude from the pad carrier plate in an axial direction, in a radial direction and/or in a tangential direction relative to the brake disc. In one variant, the contour may also be formed in.
The contour offers a further advantage in that it can form a coding of the brake pads; for example, the application-side brake pads and the rear-side brake pads may have different contours.
Alternatively, the contour may be a projection which forms a retainer for a pad retaining spring. This is particularly simple.
In yet another embodiment, each spring arm is formed, at the end, with a spring end with a thrust-imparting limb, wherein the thrust-imparting limb is in contact with a guide projection of that side of the pad carrier plate which faces toward the friction pad, wherein the thrust-imparting limb, by way of a first abutment section, lies movably with pressure against an abutment surface of the pad carrier plate, and at the same time, by way of a second abutment section arranged at right angles to the first abutment section, lies movably on a guide surface of the guide projection. In this way, simple spring ends can be used.
Here, in one embodiment, it is provided that the guide projection is of cuboidal form and is arranged below an upper edge of a corner region of the pad carrier plate on the pad side thereof. This yields a compact arrangement.
A further embodiment provides that the spreading device has at least one additional resetting element which, in addition to the engagement point/the engagement points of the spring arms, engages at a further engagement point on the respective pad carrier plate of a brake pad. This is advantageous because, in this way, an assisted resetting of the brake pads can be effected. A residual rubbing torque can thereby be prevented.
In one embodiment, the at least one resetting element may be fastened by way of one section, in a lower region of the pad carrier plate of an application-side brake pad on a thrust side of the pad carrier plate, to a retaining section, wherein the at least one resetting element is fastened by way of a further section in a lower region of a base plate of an application section of the brake caliper. In this way, it is advantageously possible for a pulling force to be exerted on the brake pad by the resetting element.
Here, the at least one resetting element may be formed as a spring element with a central section, two spring arms and two fastening sections with in each case one U-shaped lug, wherein the central section is fastened to the retaining section of the pad carrier plate, and wherein each spring arm is attached by way of the fastening section to the base plate. This is a simple and compact design. The fastening to the pad carrier plate can be performed quickly and easily for example by means of a claw-type connection to a pin of the pad carrier plate.
In a yet further embodiment, it is provided that the spreading device has at least one further additional resetting element, which is arranged between a lower region of the pad carrier plate of the rear-side brake pad and a caliper rear section of the brake caliper. It is thus also possible for the rear-side brake pad to be reset, with assistance from the further resetting element, in order to prevent a residual rubbing torque.
Here, the at least one further resetting element may be formed as a type of leaf spring with a spring body with in each case one spring end, wherein one spring end is articulated, in a lower region of the rear-side pad carrier plate on the thrust side thereof, on a holding section, and the other spring end is articulated on a fastening section of the caliper rear section of the brake caliper. In this way, a pulling force can also be exerted on the rear-side brake pad.
In an alternative embodiment, the spreading device has at least two additional recesses elements which are situated opposite one another and which are of spring form, wherein each resetting element is fastened by way of one end to a section of the spreading device and/or to a pad retaining stirrup, and wherein each free end of each resetting element is, by way of in each case one thrust-imparting limb, in contact with the respective pad carrier plate of each brake pad. This yields a simple construction, wherein a thrust force is exerted on each brake pad by a respective setting element in order to assist a resetting of the brake pads.
For this purpose, it may be provided that the at least two additional resetting elements are arranged in each case in an elongate intermediate space between a friction pad and a pad side of the respective pad carrier plate, wherein the thrust-imparting limbs are in each case in contact with the pad side of the respective pad carrier plate and each exert a thrust force on the brake pad in a direction pointing away from the brake disc. This is advantageous because the brake pads are not modified, or are modified only to a very small extent.
In the case of a brake pad set, it is provided that the bearing surface of the abutment regions is arranged at an angle with respect to a horizontal, wherein the angle lies in a range from 3 to 15°. A free relative movement of spring arm and brake pad is thus possible.
It is advantageous if the abutment surface protrudes from the pad carrier plate or is formed into the pad carrier plate, because an extensive adaptation to different installation conditions is possible in this way.
For example, one projection may be provided on the abutment surface, wherein the other projection protrudes from the abutment surface.
In another embodiment, the abutment regions may have a support section which, with the abutment surface and the bearing surface, is formed into the pad carrier plate, in order to permit a space-saving construction.
The abutment surface may also run so as to be offset, in a direction pointing away from the friction pad, relative to that side surface of the pad carrier plate which is equipped with the friction pad.
For the guidance of the spring arms, the pad carrier plates may be equipped with at least one contour which protrudes from the respective pad carrier plate or which is formed into the respective pad carrier plate. Thus, a movement travel can be easily defined, wherein a lift-off of the spring arms, for example in the event of vibrations, shocks etc., can be prevented.
A further advantage arises in that the at least one contour (50) forms a pad coding, by virtue of the application-side brake pad having a different contour than the rear-side brake pad.
In a further embodiment, the pad carrier plate of an application-side brake pad may be equipped with at least one resetting element. A coding may be possible in this way also.
Accordingly, the pad carrier plate of a rear-side brake pad may also be equipped with at least one resetting element.
One embodiment of the brake pads provides that in each case one elongate intermediate space is arranged between a friction pad and a pad side of the respective pad carrier plate, whereby simple contacting for the spring arms of further resetting elements is realized.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
The expressions “top”, “bottom”, “left”, “right” relate to the respective arrangements in the figures.
A “top side” and a “bottom side” of a brake pad 3 or of a pad carrier plate 4 always relate to the installation situation of the brake pad 3. Here, the bottom side of the brake pad 3 is situated closer in a radial direction to a brake disc axis of rotation 2a than the top side of said brake pad 3, as can be clearly seen for example from FIG. 3.